Maybe it is because they do not live in trees. Or maybe because they do.
Why are black people so creative and innovative?
Why are priests and vicars so creative and innovative?
Why are Nobel prize winners so creative and innovative?
Why is the bloke that burgled my house so creative and innovative?
Why is Jewish people singular, but other people are not?
Why is the Jewish people singular when it is made up of so many individuals?
If I had more answers than questions, I could have refuted my grandmother's allegation that people were becoming slower and denser, but as I decline into decreptitude, I cannot but concur that those younger than us, despite their tremendous scientific advances, are still unable to answer the most simple of questions, and the fault must lie with them.
It is sadly unfortunate that there is not a young person that subscribes to this forum that could provide us with evidence of their increasing knowledge, wisdom and undensity. Or at least an antonym for density.